A woman developed a case of "hairy black tongue" after taking antibiotics, according to a new report in the New England Journal of Medicine.
It can be a side effect of some antibiotics and is usually harmless and reversible.
The tongue doesn't actually grow hair. Instead, small bumps on the tongue called papillae grow longer and turn black.
The woman made a full recovery in four weeks once doctors adjusted her medication.
A woman came down with a scary-looking condition known as "black hairy tongue," according to a case report published Thursday in the New England Journal of Medicine.
The woman, 55, had been taking the antibiotic minocycline to treat an infected wound she got in a car accident, the report says. Within a week, she reported nausea and a bad taste in her mouth — and her tongue appeared to be carpeted in a disconcerting black fuzz, photos from the report show.
Dr. Yasir Hamad, an assistant professor in the Department of Medicine at the Washington University School of Medicine and an author of the report, told CNN that the patient had a "typical textbook case" of the condition.
The condition's name is a little deceiving: People who get it don't actually sprout hair on their tongues. The condition typically occurs when papillae — normal bumps on the tongue's surface — grow longer than normal because they're not shedding dead cells properly, according to the Mayo Clinic. This gives the tongue a furry appearance.
Debris, bacteria, or other microorganisms can then collect on the elongated papillae, causing the condition's trademark black discoloration. Residue from coffee, tea, and tobacco can also contribute to the dark color, according to a 2015 review in the World Journal of Gastroenterology.
Black hairy tongue can be linked to bad oral hygiene, using tobacco or irritating mouthwash, or taking antibiotics, the case report says. The reasons why it happens are still unclear, according to the 2015 review, so scientists still don't exactly know how antibiotics or other factors may trigger the condition.
Hamad told CNN that this was the first case of black hairy tongue he'd seen in 10 years of practicing medicine, but it may not be all that uncommon. Earlier studies indicate that it can occur in 0.6% to 11.3% of the population.
Thankfully, it's also benign and usually goes away once the root cause is addressed, the authors explained in the report.
"As scary as this looks, the good part is that it's actually reversible," Hamad told CNN.
The woman's doctors adjusted her medications, and after four weeks without minocycline, her tongue returned to its normal state, the report concluded.